There is absolutely nothing I can say to make an ounce of difference in your life, or the life of your son, Chance. Any attempt to say anything meaningful just seems so impotent and pointless.
I have hit the delete button several times and tried to conjure up something, anything...that would make things better.
We go back to Ol' Yeller, I believe and though we have never really been close on these boards or agreed on everything, We and others have shared a decade or more on these boards and it is pretty damn hard not to get attached or feel connected to people -- even if you have never met or even know their name in real life.
As one man to another and one father to another -- I wish you the best on this unimaginably difficult journey. I am grateful that you have been able to enjoy these 13 years together and that he has reached an age/maturity level where you guys can have an opportunity to discuss his hopes and dreams. You can have conversations about things that will help bring about some sense of closure.
I am not going to tell you to hang tough, don't give up or what not. Because, frankly, I am not sure I would be strong enough to continue living were I in your shoes. But, If I could offer up anything of value, I would encourage you to discuss with your son things or something you can do to honor his life in some meaningful way. If you have any desire to live after your son passes, maybe you will find strength, comfort and peace in knowing that you are living in a manner that allows the beauty and spirit of your son to live on through you.
I will be thinking of you and your family.